Actually, the silversides sold as fish food (arctic pond smelt) are also harvested for human consumption. It's just that I've often seen packages of little fish sold in stores around my area, called "silversides" and those were true smelt. Not the safe kind. You can only tell the difference by the fins. Smelt and Baitfish - RecFIN

Silversides (safe arctic pond smelt) do not have an adipose fin while Osmerids (true smelt containing thiaminase) do have an adipose fin.